The present invention relates to a device for the programmed control of operative sequences, particularly suitable for cassette-type tape recorders.
In a cassette-type tape recorder, in order to automatically set a cassette into its operative position and reject it from the recorder, it is necessary to utilize a device, which can store or memorize the operative sequences which relate to some or all of the following controls to be effected in the right time sequence:
slipping-in of the cassette towards the inside of the apparatus;
downward pull of the cassette to the operative position, where the cassette reels are engaged by a tape transport mechanism;
entering of the magnetic head and of the pressure roller, located on a suitable support, in the opposite openings of the cassette;
setting in the operative position of the control key for the fast forward and fast rewind movements of the tape.
While the control sequence must take place in the aforementioned, i.e., direct succession when the recorder is being prepared for operation, the same sequence must take place in a reverse succession when the operation of the recorder is being stopped and the cassette is to be removed.
In general, it is desirable that one of the two operative sequences, i.e. the sequence in the direct succession or the sequence in the reverse succession, takes place under the control of an elastic element, while the other sequence may be realized through a manual key or by a servomotor.
In the design of said devices for the programmed control of operative sequences, two main problems have been encountered.
The first problem relates to the centralization of the control of the actuating devices of the controls into a single element to assure the desired operative sequence.
Said centralization is hampered in the first place by the fact that some of the desired movements must be linear while others must be angular; and in the second place by the fact that the actuating devices are generally disposed on different planes and are generally disposed, with respect to each other, at different angular positions. An additional obstacle to the centralization is given by the receiprocal distances of the various devices actuating the movements.
Another problem is that of reducing as much as possible the difference between the percentage elongation of the elastic element at the beginning and at the end of the operative movement, in order to have a substantially constant force during the entire operative sequence which it controls. In other words, the final force exercized by the almost run-down elastic element must be only slightly less than the initial force exercized by the fully charged elastic element.
The reduction of the difference between the percentage elongations of the elastic element is hampered by the limitation of the dimensions of the recorder, dimensions which must always be respected, in contrast to the fact that the elastic elements must have dimensions sufficient to provide the force necessary for the operation of the apparatus.
In Italian Pat. Nos. 848,887 and 1,004,253 (U.S. Pat. Nos. 3,669,455 and 4,014,041) there have been described two devices of this type, in the first of which both the direct succession and the reverse succession are realized manually. The device described in Italian Pat. No. 1,004,253 (U.S. Pat. No. 4,014,041) comprises an elastic element which effects the direct or setting succession in an automatic manner at the moment of introduction of the cassette, while a manual control provides for the execution of the reverse succession to eject the cassette at the end of the play cycle. In both of the known devices a programming element is moved linearly to realize the right operative sequence.
From the German Pat. No. 27 04 354 (corresponding to Italian Patent Application No. 47,849 A 76) and issued U.S. Pat. No. 4,128,015 is also known a device of the type in question, in which the programming element is moved linearly by a wheelwork connected to the motor of the recorder, during the execution of the direct sequence. During this phase, the motor also charges a linear elastic element, the discharge of which elastic element will then be utilized to effect the reverse sequence of the operations when it is desired to interrupt the operation of the recorder or also simply when the power lacks. However, such known devices suffer from the disadvantages of a poor centralization and a great difference between the percentage elongation of the spring.